1. Field of the invention
The present invention relates to electrical engine-generator sets and more particularly to methods for performing diagnostic tests on an electrical engine-generator set.
2. Description of the Related Art
Homes and commercial buildings commonly have an electrical backup generator system in which an internal combustion engine drives an electrical alternator that provides electricity when power is unavailable from an electric utility company. A controller responds to the interruption of the utility company power by automatically starting the engine. When the alternator reaches the nominal speed at which electricity properly is produced, the controller activates an automatic transfer switch to disconnect selected electrical circuits within the building from the utility power lines and connect those circuits to the output of the alternator. When the controller senses restoration of the utility company power, the automatic transfer switch operates to reconnect the building electrical circuits to the utility company lines and then turn off the engine.
Most of these backup electrical generator systems can sit idle for long periods of time, e.g. many months, between events when the backup electricity is required. During such periods of inactivity, problems may arise that adversely affect the ability of the generator system to produce power when needed. This is especially true with home installations that usually are not tested by the homeowner. As a result, it is desirable to have the backup generator system automatically perform self-diagnostic tests on a periodic basis. If problems are detected, the controller should alert building occupants and remote service personnel so that servicing of the system can be performed in a timely manner.
Engine-generator sets previously were periodically operated at less than full speed in order to exercise the mechanical components without producing a high noise level. Nevertheless, diagnostic tests heretofore were performed only by operating the engine-generator set at full normal speed for a prolonged time in order to determine that the engine and alternator were performing within predefined operational tolerances and that the control and regulatory systems were functioning properly. Such full speed operation, however, produced a high level of noise, which was found to be objectionable to homeowners and occupants of other types of buildings. As a result, it is desirable to be able to perform full diagnostics on the engine-generator set without producing an objectionable level of noise.
In some instances, an engine generator operated at low speed for the purpose of warming up or circulating engine fluids. Diagnostics were later performed at full speed with some level of electrical loading.
In addition, generators were exercised at a preset time as determined by an automated transfer switch controller or separate modular timer.
The results of the diagnostic operation and alerts, when faults were detected, were provided to remote locations by means of expensive communication adapters that sent the generator information to building control systems and eventually via a communication link to remote sites. The costs and expertise required to functionally test existing backup generator systems limited usefulness to customers and ability to provide timely service.